Tropical and temperate differences in the trophic structure and aquatic prey use of riparian predators

Abstract

The influence of aquatic resource‐inputs on terrestrial communities is poorly understood, particularly in the tropics. We used stable isotope analysis of carbon and nitrogen to trace aquatic prey use and quantify the impact on trophic structure in 240 riparian arthropod communities in tropical and temperate forests. Riparian predators consumed more aquatic prey and were more trophically diverse in the tropics than temperate regions, indicating tropical riparian communities are both more reliant on and impacted by aquatic resources than temperate communities. This suggests they are more vulnerable to disruption of aquatic–terrestrial linkages. Although aquatic resource use declined strongly with distance from water, we observed no correlated change in trophic structure, suggesting trophic flexibility to changing resource availability within riparian predator communities in both tropical and temperate regions. Our findings highlight the importance of aquatic resources for riparian communities, especially in the tropics, but suggest distance from water is less important than resource diversity in maintaining terrestrial trophic structure.

Global patterns of allochthony in stream–riparian meta‐ecosystems

“…Another meta‐analysis found that aquatic insect emergence patterns vary with latitude, being seasonally constrained with small aseasonal fluctuations in the tropics to large seasonal peaks at the highest latitudes (Nash, Zorzetti, et al., 2023). Indeed, a more consistent flux of allochthonous resources could lead to consumer communities that are more reliant on and impacted by them, which is what a companion study that compared riparian spiders in tropical and temperate zones found (Nash, Kratina, et al., 2023).…”